DESCRIPTION: (Applicant's abstract) Functional nerve stimulation (FNS) is a method to restore lost function to patients with spinal cord injury. Nerve electrodes offer many advantages over muscular stimulation, including control of several muscles with one device, lower power requirements, and the potential for recording afferent neural signals. Progress in this area, however, has been hampered by the lack of a truly safe and selective electrode for stimulation of, and recording from, peripheral nerves. Intraneural electrodes have considerable advantages in terms of selectivity but disrupt the perineurium, the protective membrane surrounding nerve fascicles. Current cylindrical cuff electrodes cause little nerve damage, but can not activate axons located in the center of the nerve without stimulating more superficial fibers as well. In this proposal, a new extraneural electrode designed to increase the surface area of the nerve/electrode interface is proposed. Normally, the geometry of peripheral nerves is determined by their environment. This nerve cuff will create an environment to hold the nerve flat, allowing more area for contact placement and bringing deep axons closer to extraneural contacts. This study has been divided into five primary aims and objectives. The first objective is to show that maintaining peripheral nerves in a flat geometry allows stimulation selectivity without causing nerve damage. Electrodes will be implanted chronically on the cut sciatic nerve to test both electrode safety and stimulation selectivity. The second aim is to show that fascicles can also be reshaped in order to generate sub-fascicular selectivity. Fascicle reshaping electrodes will be implanted in chronic cat preparations to test the safety and selectivity of this cuff design. The third aim is to design a controller capable of generating specific torques with this multiple contact electrode. Artificial neural networks (ANNs) will be used to control this non-linear, time varying system, and the controller will be tested with computer simulations, acute experiments, and chronic experiments. The forth aim is to show that nerve reshaping allows selective recording of neural activity, providing a method to determine which axons within the nerve are firing. Computer models, acute experiments, and chronic experiments will be combined to determine the feasibility of selective recording. Finally, the last aim is to determine the characteristics of and implement an optimal wireless design of the Flat Interface Nerve Electrode (FINE). Computer models will guide cuff design, and the optimum cuff will be controlled by hermetically sealed microcircuitry powered by an externally located coil. The end-product of this project will be a FNS system consisting of a selective, wireless electrode for neural stimulation and recording, as well as an adaptive controller for that electrode. This electrode could significantly improve the ability of current neural prosthetic devices to restore neuromuscular function.